A major challenge in composite materials is to find a polyamide resin which meets the following specifications:                High Tg for a wide range of operating temperatures;        The lowest possible Mp, so as to be readily processable without recourse to excessively specific mold metallurgies;        A very good crystallization capacity in order to be able to be rapidly demolded and thus to be compatible with intensive production cycles, such as those used in the motor vehicle industry;        A high rigidity, including under hot conditions, so as to be able to obtain the highest possible moduli of the final material.        
Document CN104211953 describes a polyamide composition comprising from 30% to 99.9% by weight of a polyamide resin comprising from 60 to 95 mol % of 10T, from 5 to 40 mol % of 5′T, 5′ corresponding to 2-methyl-1,5-pentamethylenediamine, from 0% to 70% by weight of a reinforcing filler and from 0.1% to 50% by weight of an additive.
The polyamide resin has a melting point above 260° C.
EP 550 314 describes, among its examples, (nonreactive) copolyamide compositions in a search for melting points of greater than 250° C. and limited Tg values, with the majority of the examples cited having an excessively low Tg (<80° C.) or an excessively high Mp (>300° C.).
EP 1 988 113 describes a molding composition based on a 10T/6T copolyamide with:                40 to 95 mol % of 10T        5 to 40% of 6T.        
Polyamides with a high melting point of greater than 270° C. are targeted in particular. The examples mentioned and FIG. 1 teach that the melting point of these compositions is at least approximately 280° C.
WO 2011/003973 describes compositions comprising from 50 mol % to 95 mol % of a unit based on a linear aliphatic diamine comprising from 9 to 12 carbon atoms and on terephthalic acid and from 5% to 50% of unit combining terephthalic acid with a mixture of 2,2,4- and 2,4,4-trimethylhexanediamine.
US 2011/306718 describes a process for the pultrusion of reactive aliphatic polyamides having low Tg values in combination with chain extenders of polymeric structure bearing several (and many more than 2) anhydride or epoxide functions. This document does not describe any nonpolymeric extender.
WO 2014/064375 describes in particular a PA MXDT/10T which exhibits an excellent compromise between the various characteristics described above. Unfortunately, the m-xylene diamine (MXD) monomer used is highly subject to side-reactions, giving rise in particular to the formation of branching.
The drawbacks of the prior art, with the absence of a good compromise between the mechanical performance levels and the processing ability (ease of transformation) at lower temperature with a shorter production cycle time are overcome by means of the solution of the present invention which targets semi-crystalline PA compositions having an excellent compromise between high mechanical performance levels (mechanical strength), in particular under hot conditions, and easy processing. It in fact has a high rigidity and has a glass transition temperature >120° C., a Mp<290° C., and also an excellent crystallization capacity (Mp−Tc<40° C.), which makes it a matrix of choice for composite applications, in particular for the wind power, motor vehicle or aeronautical industry.
More particularly, in the case of the reactive compositions, it is sought to have faster reaction kinetics while at the same time having a rate and/or temperature of crystallization of the polymer formed that are also higher.
The choice of a semi-crystalline polyamide polymer, as matrix of the composite material of the invention, has the advantage, compared with amorphous polyamides, of significantly improved mechanical performance levels, especially at elevated temperature, such as creep resistance or fatigue resistance. In addition, having a melting point above 200° C. has the advantage in the motor vehicle industry of being compatible with treatments by cataphoresis, which a structure of amorphous PA type does not permit. As for the amorphous materials, a Tg of greater than or equal to 90° C. is sought so as to ensure good mechanical properties for the composite over the entire working temperature range, for example up to 90° C. for the wind power industry, up to 100° C. for the motor vehicle industry and up to 120° C. for the aeronautical industry. Conversely, an excessively high melting point, in particular of greater than 290° C., is on the other hand harmful as it requires processing the composite at higher temperatures with constraints in terms of molding equipment to be used (and associated heating system) and excessive consumption of energy with, in addition, risks of thermal degradation due to heating at temperatures higher than the melting point of said polyamide, with as a consequence the modification of the properties of the final thermoplastic matrix and of the composite which results therefrom. The crystallinity of said polymer must be as high as possible, but with a melting point Mp that is not too high (Mp<290° C. and more particularly <280° C.) in order to optimize the mechanical performance levels and the crystallization rate and/or the crystallization temperature must be as high as possible, in order to reduce the molding time before ejection of the molded composite part with a selective choice of the composition of said semi-crystalline polyamide.